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Faculty Sponsor

Dr. Punya Nachappa


Department of Biology

University Affiliation

Indiana University – Purdue University Fort Wayne


Soybean (Glycine max) is an important crop due to its versatility as a food source as well as various applications in industries such as biofuel and textiles. In Indiana alone, there are 40,000 farmers growing soybeans on 5.4 million acres, contributing approximately $ 1.5 billion to state’s economy per year. In 2012, however, the state of Indiana received less than 1 inch of precipitation in the months of June and July, which severely impacted agriculture, including soybean. Soybean yields dropped significantly to 39.3 bushels per acre, the lowest since 2003. In addition to the direct impact of drought stress on yield, drought is also thought to promote outbreaks of insect pests and pathogens. On soybeans, the soybean aphid (Aphis glycines) is a major pest contributing to reduced yields not only due to direct feeding but also transmits various economically important viruses such as Soybean mosaic virus. The objectives of our study are to: (1) determine the effects of drought stress on soybean aphid populations and (2) determine the impact of drought stress on the activation of soybean plant defense pathway genes. To determine the effect of drought stress on soybean aphid, we placed twenty aphids on soybean plants that were subjected to various levels of drought stress (30%, 50%, 70%, and 100% soil water content) in a growth chamber. The population growth rate of soybean aphids was monitored for 7 days. Preliminary results indicate that aphid populations are significantly greater on plants exposed to 70% soil water content than 30%, 50%, and 100% (P<0.015). Reverse-transcriptase-PCR analysis of soybean plant defense genes in response to drought stress and/or aphid infestation indicated distinct gene expression patterns. Knowledge of the ecological and molecular mechanisms underlying drought stress on insect pests and plant yield can be applied to development of sustainable crop management practices.


Biology | Life Sciences

Effect of drought stress on population growth rate of an insect pest, soybean aphid (Aphis glycines Matsumura)

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